MPlab Soruce Code Help!!

w0t3rf15h

要怎样写以下的code?

A=256*B+C

D=A*0.4882125

pic data sheet 里只有ADD,
那乘要用什么？
还有0.488要怎样表达？
hex,dec,bin都不能有0.xxx de

GeMan

microchip 有 fix point multiplication ＆ division code。

application note AN６１７：
http://www.microchip.com/stellen ... mp;appnote=en010962

documentation：
http://ww1.microchip.com/downloads/en/AppNotes/00617.pdf

source code：
http://ww1.microchip.com/downloads/en/AppNotes/00617.zip


＞＞A=256*B+C
＞＞D=A*0.4882125

如果 B， C 是 integer 那就容易， 用 fix point multiplication。

然后用 fix point multiplication ＆ division：
D ＝ （A ＊ ４８８２１２５）／１０００００００

w0t3rf15h

原帖由 GeMan 于 28-11-2006 08:15 AM 发表
microchip 有 fix point multiplication ＆ division code。

application note AN６１７：
http://www.microchip.com/stellen ... mp;appnote=en010962

docu ...

不懂它的意识，我用pic16f873,
他给的只有16cXXX

A=256*B+C

For this u hav to write a sub routine for multiplication. This can be done using successive addition. If ur value 256 is fixed then u need not want to multiply it. Simply put two zeros in right side.

For example: if B=0x23, then 256*B will be 0x2300, that is two zeroes in right side. Then add C with ur answer. if C=0x45, U will get A=0x2345.

D=A*0.4882125

Remove Decimal point and take the hex value, Multiply it and convert back to decimal and then put the decimal.

Example: In ur equation 0.4882125 , after removing the point u get 4882125, take hex manually, 4882125=0x4A7ECD
change ur equation as
D=A*0x4A7ECD
Then multiply u get 0xA436A3441
Convert it into decimal, u get 44080706625
Then put the decimal point 7 places from right , then u get 44080.706625 ..

以上的能用ma?

GeMan

－－不懂它的意识，我用pic16f873,
－－他给的只有16cXXX
＃＃一样的。



－－A=256*B+C
－－For this u hav to write a sub routine for multiplication. －－This can be done using successive addition. If ur value －－256 is fixed then u need not want to multiply it. Simply －－put two zeros in right side.
－－For example: if B=0x23, then 256*B will be 0x2300, that －－is two zeroes in right side. Then add C with ur answer. －－if C=0x45, U will get A=0x2345.
＃＃如果， ２５６ 是 constant， B ＆ C 是 integer 就可以这么做


－－D=A*0.4882125
＃＃这个就有问题， 要用 fix point multiplication ＆ division：
D ＝ （A ＊ ４８８２１２５）／１０００００００